/* Copyright (c) 2020 XEPIC Corporation Limited */
/*
 * Copyright (c) 2000-2011 Stephen Williams (steve@icarus.com)
 *
 *    This source code is free software; you can redistribute it
 *    and/or modify it in source code form under the terms of the GNU
 *    General Public License as published by the Free Software
 *    Foundation; either version 2 of the License, or (at your option)
 *    any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 * USA.
 */

#include <assert.h>
#include <math.h>
#include <string.h>

#include "sys_priv.h"

static PLI_INT32 sys_time_calltf(ICARUS_VPI_CONST PLI_BYTE8* name) {
  s_vpi_value val;
  s_vpi_time now;
  vpiHandle call_handle;
  vpiHandle mod;
  int units, prec;
  long scale;

  call_handle = vpi_handle(vpiSysTfCall, 0);
  assert(call_handle);

  mod = sys_func_module(call_handle);

  now.type = vpiSimTime;
  vpi_get_time(0, &now);

  /* All the variants but $simtime return the time in units of
     the local scope. The $simtime function returns the
     simulation time. */
  if (strcmp(name, "$simtime") == 0)
    units = vpi_get(vpiTimePrecision, 0);
  else
    units = vpi_get(vpiTimeUnit, mod);

  prec = vpi_get(vpiTimePrecision, 0);
  scale = 1;
  while (units > prec) {
    scale *= 10;
    units -= 1;
  }

  assert(8 * sizeof(long long) >= 64);
  {
    long frac;
    long long tmp_now = ((long long)now.high) << 32;
    tmp_now += (long long)now.low;
    frac = tmp_now % (long long)scale;
    tmp_now /= (long long)scale;

    /* Round to the nearest integer, which may be up. */
    if ((scale > 1) && (frac >= scale / 2)) tmp_now += 1;

    now.low = tmp_now & 0xffffffff;
    now.high = tmp_now >> 32LL;
  }

  val.format = vpiTimeVal;
  val.value.time = &now;

  vpi_put_value(call_handle, &val, 0, vpiNoDelay);

  return 0;
}

/* This also supports $abstime() from VAMS-2.3. */
static PLI_INT32 sys_realtime_calltf(ICARUS_VPI_CONST PLI_BYTE8* name) {
  s_vpi_value val;
  s_vpi_time now;
  vpiHandle callh;
  vpiHandle mod;

  callh = vpi_handle(vpiSysTfCall, 0);
  assert(callh);

  mod = sys_func_module(callh);

  now.type = vpiScaledRealTime;
  vpi_get_time(mod, &now);

  /* For $abstime() we return the time in second. */
  if (strcmp(name, "$abstime") == 0) {
    PLI_INT32 scale = vpi_get(vpiTimeUnit, mod);
    if (scale >= 0)
      now.real *= pow(10.0, scale);
    else
      now.real /= pow(10.0, -scale);
  }

  val.format = vpiRealVal;
  val.value.real = now.real;
  vpi_put_value(callh, &val, 0, vpiNoDelay);

  return 0;
}

void sys_time_register(void) {
  s_vpi_systf_data tf_data;
  vpiHandle res;

  tf_data.type = vpiSysFunc;
  tf_data.tfname = "$time";
  tf_data.sysfunctype = vpiTimeFunc;
  tf_data.calltf = sys_time_calltf;
  tf_data.compiletf = sys_no_arg_compiletf;
  tf_data.sizetf = 0;
  tf_data.user_data = "$time";
  res = vpi_register_systf(&tf_data);
  vpip_make_systf_system_defined(res);

  tf_data.type = vpiSysFunc;
  tf_data.tfname = "$realtime";
  tf_data.sysfunctype = vpiRealFunc;
  tf_data.calltf = sys_realtime_calltf;
  tf_data.compiletf = sys_no_arg_compiletf;
  tf_data.sizetf = 0;
  tf_data.user_data = "$realtime";
  res = vpi_register_systf(&tf_data);
  vpip_make_systf_system_defined(res);

  tf_data.type = vpiSysFunc;
  tf_data.tfname = "$stime";
  tf_data.sysfunctype = vpiIntFunc;
  tf_data.calltf = sys_time_calltf;
  tf_data.compiletf = sys_no_arg_compiletf;
  tf_data.sizetf = 0;
  tf_data.user_data = "$stime";
  res = vpi_register_systf(&tf_data);
  vpip_make_systf_system_defined(res);

  tf_data.type = vpiSysFunc;
  tf_data.tfname = "$simtime";
  tf_data.sysfunctype = vpiTimeFunc;
  tf_data.calltf = sys_time_calltf;
  tf_data.compiletf = sys_no_arg_compiletf;
  tf_data.sizetf = 0;
  tf_data.user_data = "$simtime";
  res = vpi_register_systf(&tf_data);
  vpip_make_systf_system_defined(res);

  tf_data.type = vpiSysFunc;
  tf_data.tfname = "$abstime";
  tf_data.sysfunctype = vpiRealFunc;
  tf_data.calltf = sys_realtime_calltf;
  tf_data.compiletf = sys_no_arg_compiletf;
  tf_data.sizetf = 0;
  tf_data.user_data = "$abstime";
  res = vpi_register_systf(&tf_data);
  vpip_make_systf_system_defined(res);
}
